The present invention relates to a mechanism for operating valves in an internal combustion engine in an automobile.
In internal combustion engines, unless countermeasures are taken, a considerable portion of the driving power of the valve operating mechanism is lost due to friction between the actuation spindle of the mechanism, which is customarily a camshaft, and the component of the mechanism which rests against the actuation spindle, for example, a rocker arm, a drag lever, a tappet, or the end of a valve stem.
U.S. Pat. No. 3,795,229 and Great Britain Pat. No. 960,396 disclose arrangements wherein a roller is provided on a tappet or lever in order to decrease friction. A decrease in friction is attained in these arrangements, but there is a resulting disadvantage. Specifically, the mass to be moved by the valve spring during valve closing is increased by the mass of the roller. Therefore, stronger valve springs are necessary, and the size of the valve operating mechanism must be increased accordingly. Consequently, part of the gain in the driving power of the valve operating mechanism due to the decrease in friction that results because of the use of a roller is lost in work efficiency of the valve operating mechanism.